This invention is concerned with security systems.
It is commonly known to construct boundary fences using cables or wires running between adjacent posts. Such fences can, for example, be used to contain animals within a field or prevent unauthorised entry into an area delimited by the fence. However, there are many such cases where it would be extremely desirable or even essential to be provided with some means of warning when any attempt, even unsuccessful, has been made to cross the boundary.
In this specification, the terms "strip" and "strand" will be used. In the present context, "strip" means a long narrow band of small thickness. "Strand" on the other hand has a broader meaning so as to include also other cross-sectional shapes.